Adjustable choke



y 1954 E. c. INGRAHAM ,069

ADJUSTABLE CHOKE Filed July 19, 1946 INVENTOR ELMER C. INGRAHAM ATTORNEY Patented July 27, 1954 UNITED STAT' ATENT OFFICE ADJUSTABLE CHOKE Navy Application July 19, 1946, Serial No. 684,997

9 Claims. 1

This invention relates in general to radio frequency chokes and more particularly to adjustable radio frequency chokes for use in radio frequency transmission systems.

Generally, radio frequency (hereinafter abbreviated R.-F. joints in guided wave systems are of such construction that the joining components may be fastened together securely. This requires that the choke joints have some flexibility so the two sections may be positioned opposite each other and drawn together. However, in certain types of radio frequency plumbing, waveguide sections are milled or otherwise machined. from a solid casting. In such castings it is often impossible to allow for flexibility in an R..-F. joint sothat two sections cannot be drawn together in the usual manner.

It is thus an object of this invention to provide an adjustable radio frequency choke joint for use in connection with guided wave transmission systems.

Another object of this invention is to provide an adjustable radio frequency choke joint for non-flexible sections of radio frequency plumbing.

These and other objects will be apparent from the following specification when taken with the accompanying drawing which illustrates one form of the invention.

Choke joints are used in waveguides and R.F. plumbing to prevent losses and reflections at the junction of two sections. The most common type R.-F. choke joint in use consists of two flanges around the RAE, path. One flange is made with a flat surface, and an L-shaped groove is cut into the other around the energy path. This L-shaped groove or cavity acts as a onehalf wavelength transmission line. The conduction current in the walls of the guide flows into this cavity. The open gap left between the walls of the two sections by the l.--shaped groove is thus one-half wavelength from the shorted end of said groove and thus the walls of the two sections appear to be connected together. The actual contact point between the two flanges occurs at a point one-quarter wavelength from the shorted end of the L-shape-d groove and the current there is substantially zero so the joint thus can have a high resistance.

In such a joint the R.-F. energy paths of the sections are lined up and the flanges are drawn together to keep the leakage and reflections at the joint at a minimum.

In certain cases, such as the one described earlier using solid castings, no flexibility is allowed in the joint.

This invention as illustrated herein provides an adjustable choke joint for a TR. tube mounted in a rigid waveguide where the sections do not quite meet but is readily adaptable to prevent losses and reflections in any waveguide joint where the two sections cannot be drawn tightly together.

The-invention will now be described with reference to the drawing. Waveguide section 39 is a solid block which has been milled out to hold a TR tube 32. TR tubes are constructed with a given tolerance in width 34' and the groove milled in waveguide section 36 is cut to width 35 within a given tolerance. There will thus be a slight difference in fit betweenv different TR, tubes.

TR tube 32 is fastenedflush at face 38 to a surface of section 30. Choke joint 48 of conventional design (described above) prevents the loss of energy between these two surfaces; There generally is a small gap between the face 42 of tube 32' and the surface it of the waveguide section 39. To compensate for such a gap and to maintain contact between the wall of the waveguide section as and TR tube 52 a circular groove is is milled in section 38 just outside of conventional type choke groove 46. An externally threaded sleeve 58 is shrunk or press fitted into groove 63. An internally threaded ring 52 having a knurled surface 5% is fitted over sleeve 5B. A. section of waveguide 39 is milled out at 5| to provide an open slot, as shown, to expose knurled surface 54 of adjustable ring 52. This allows adjustment of ring 52 when the joint is assembled. Ring 52 fits against another ring 56 which is made of a slightly com pressible' metal or other suitable conductive material'. against the surface 42' of tube '52 and thus maintain contact with the face 42.

The gap between the surfaces .2 and G4 under normal conditions is quite small and does not cause any apprc-iciab'l'e electrical loss. The adjustable ring 5 5' contacting both these surfaces maintains the electrical loss at the joint at a minimum.

Thus it may be seen that this invention provides means for adjusting any R'.-F. choke joint where: the sections to be joined do not quite meet and cannot for reasons of mechanical construc tion be drawn into contact.

It is believed that the construction and operation, as well as the advantages of this improved radio frequency choke joint will be apparent from the foregoing detailed description thereof. It will also be apparent that while the invention has been shown and described in a preferred form Sleeve 52' is adjusted to force ring 56' changes may be made in the construction disclosed without departing from the spirit of the invention as sought to be defined in the following claims.

What is claimed is:

1. A coupling arrangement for use in the propagation of ultrahigh frequency energy comprising, in combination, a waveguide section having an energy transmission passage therein, said section being provided with a cut-out portion intersecting said energy passage and perpendicular thereto whereby confronting first and second face portions are formed which include as parts thereof said energy passage, a circular groove cut in said first face portion surrounding the en ergy passage associated therewith, an adjustable ring disposed partially within said groove and adapted to be displaced by variable amounts beyond said face whereby the width of said cut-out portion is changed to permit the insertion of variably dimensioned waveguide sections between said ring and said second face.

2. A coupling arrangement for use in the propagation of ultrahigh frequency energy comprising, in combination, a first wave guide member having an energy transmission passage therein, said member being provided with a peripheral slot intersecting said energy passage and per pendicular thereto whereby first and second confronting surfaces having as parts thereof said energy passage are formed, a groove in said first surface surrounding the energy passage associated therewith, a conductive ring member disposed within said groove, a second wave guide member having a length less than the width of said slot, said second wave guide member being positioned within said slot with its energy passage coextensive with that of said first wave guide member, means for securing one end of said second member to the second surface of said first wave guide, said ring member and said groove having cooperating threaded portions whereby rotation of said ring causes it to project from said first surface into abutment with the free end portion of said second wave guide member to thereby produce a completely enclosed energy passage between said wave guide members.

3. A coupling arrangement, as defined in claim 2, wherein said first surface has cut therein a second groove concentric with said first groove, said second groove and the projecting portion of said ring member defining in combination with a portion of said first surface and a portion of the free end of said second wave guide an L- shaped resonant cavity whereby the contact impedance between said first surface, said ring member and said second wave guide section is minimized.

4. A coupling arrangement, as defined in claim 3, wherein an L-shaped resonant cavity is provided at the junction of said second surface and the second wave guide member whereby the contact impedance therebetween is minimized.

5. A coupling arrangment for use in propagation of ultrahigh frequency energy comprising, in combination, a first wave guide section having an energy transmission passage therein, said section being provided with a peripheral slot intersecting said passage and perpendicular thereto whereby first and second confronting surfaces are formed having as parts thereof said energy passage, a groove cut in said first surfaces surrounding the energy passage associated therewith, an adjustable conductive ring disposed partially within said groove, a second wave guide member, means for securing one end of said second wave guide member to said second surface so that the respective energy passages in the second guide member and the second surface are in coaxial alignment, said second wave guide member having a length less than the width of said slot whereby a gap is present between the first section and the free end of said second wave guide member, and means for extending said ring into abutment with the free end of said second member whereby a completely enclosed energy transmission passage is produced with the ring member supplying the necessary closing length.

6. A coupling arrangement, as defined in claim 5, wherein said first surface has cut therein a second groove concentric with said first groove, said second groove and the extending portion of said ring defining in combination with a portion of said first surface and a portion of the free end of said second wave guide, an L-shaped resonant cavity whereby contact impedance between said first surface, said ring member and said second wave guide member is minimized.

7. A coupling arrangement, as defined in claim 6, wherein an L-shaped resonant cavity is provided at the junction of the second surface and the second wave guide member whereby the contact impedance therebetween is minimized.

8. A coupling arrangement, as defined in claim 5, wherein said means for extending said ring comprises cooperating threaded portions formed in said ring and in said groove whereby rotation of said ring causes it to extend beyond said first surface.

9. A coupling arrangement, as defined in claim 5, wherein the portion of said ring abutting the free end of said second wave guide member is of compressible material, thereby insuring intimate contact between the ring and the second wave guide member.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 199,312 Perkins Jan. 15, 1878 255,163 Goldschrnid Piaf. 21, 1882 699,174 Hoppes May 6, 1902 882,350 Shaughnessy Mar. 17, 1908 969,311 Van Houten Sept. 6, 1910 1,202,196 Lewis Oct. 24, 1916 2,430,445 Aarnodt NOV. 11, 1947 2,433,011 Zaleski Dec. 23, 1947 2,473,724 Okress et a1 June 21, 1949 2,476,621 Okress July 19, 1949 2,480,194 Montgomery Aug. 30, 1949 2,513,067 Stephan June 27, 1950 

